A volume of information to be handled by a portable information device today, has been growing to be remarkably huge, along with the improvement in a screen display device and/or a recording medium, and along with the popularization of multimedia usage. Under such circumstances, becoming popular is a cradle that serves as an interface. Using the cradle, the portable information device can easily be charged, and can simply exchange information with external devices. Such a cradle includes a power interface and a communication interface each having a metal connector. The cradle plays a role as a relaying device (transponder) that enables the portable information device and the external device to access each other.
It should be noted that the following patent documents 1 through 3 are known as the prior arts related to the present invention.
Patent document 1, i. e., Japanese Unexamined Patent Publication No. 2001-142837 (Tokukai 2001-142837; published on May 25, 2001), discloses an interface device for connecting a portable information terminal device to external devices. An object of the interface device is to simultaneously connecting a plurality of the external devices, without causing an inadequate connection. More specifically, according to the interface device, an infrared light receiving/emitting section is provided in a terminal receiving section of a cradle serving as a relaying device for the portable information terminal device and the external devices. The infrared light receiving/emitting section is provided for performing a non-contact communication, with the use of an infrared light emitting signal, with the portable information terminal device mounted on the terminal receiving section. Further, a USB connection terminal and an RS232C connection terminal are provided as connection terminals for the external devices, so that data signals which are transmitted to or received from, via the infrared light emitting signal, the portable information terminal device are sent to an external personal computer and/or a modem, via a USB interface or an RS232C interface. Moreover, the interface device detects whether or not the external devices are connected with the USB connection terminal, and whether or not the external devices are connected with the RS232C connection terminal, and informs the portable information terminal device of connection results thus detected.
Patent document 2, i. e., Japanese Unexamined Patent Publication No. 2002-23896 (Tokukai 2002-23896; published on Jan. 25, 2002), discloses an electronic device whose object is to surely perform data processing with respect to data whose power consumption is large. More specifically, when (i) a connection with a cradle is detected in accordance with an output from a cradle detecting section which detects whether or not a portable information device is placed on a receiving section of the cradle, and (ii) power supply from an external power source is confirmed in accordance with an output signal from a power source detection control section, data processing means carries out the data processing, which requires large power consumption, such as encoding process which has been registered by writing in flag data.
Patent document 3, i.e., Japanese Unexamined Patent Publication No. 252017/1999 (Tokukaihei 11-252017; published on Sep. 17, 1999) discloses a portable wireless terminal having infrared data communication function, whose object is to reduce power consumption of infrared data communication by detecting an infrared data communication partner so that infrared light emission power is appropriately controlled, even when communication distance changes. More specifically, the portable wireless terminal is provided with (i) an infrared data communication section for transmitting and receiving signals in an infrared frequency band, (ii) a communication partner detecting section for detecting information indicative of the infrared data communication partner, and (iii) a control section for controlling light emission power of the infrared data communication section in accordance with the information, indicative of the infrared data communication partner, which has been detected by the communication partner detecting section.
However, in each of the foregoing cradles, the terminal connecting terminal for the portable information device is a socket-type connector. This causes the problems that the socket-type connector becomes fragile by frequently repeating plugging and unplugging, and an inadequate connection is easily brought about.
Meanwhile, a size of the portable information device has been reduced to enhance mobility. In contrast, the power consumption has been growing, due to development of a screen display device, and development of a multi-media related function, in the portable information device. Under such circumstances, it is necessary to efficiently use power to carry around the portable information device for a long time.